A model for delivering hosted services over a network such as the Internet that has gained fraction in recent years is commonly referred to as virtualization. Virtualization is the delivery of computing as a service rather than a product, whereby shared resources, software, and/or information are provided to computers and other devices as a utility (like the electricity grid) over a network (typically the Internet). Virtualization may use public service networks, private service networks or hybrid service networks. Hosted services may fall into a variety of categories such as, for example: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS).
Virtualized computing may generally be available on demand, often by the minute or the hour, for example. A user may use as much or as little of a service as desired. Virtualized computing services are often managed by a computing service provider. Virtualized computing typically involves some degree of distributed computing. Use of virtualized computing in the enterprise may reduce expenditures on computing infrastructure such as hardware, application and bandwidth costs, as well as maintenance. Virtualized computing and software as a service (SaaS) infrastructures may present a cost effective solution for meeting computing needs.
In general, there exist public and private service networks. Public service networks are often accessible from any location, with the appropriate credentials, and provide computational resources to any interested customers. In contrast, a private service network is often privately-owned and operated. Private service networks generally serve a limited population of users, such as employees of a large corporation that owns the compute infrastructure, for example. Virtual private service networks can be created from public service network resources.